Introduction. Patients with unipolar depression show impaired
performance on the Tower of
London planning task. Positron emission tomography, which has previously
state blood flow abnormalities in depression, was used to investigate neural
with performance of this task in depressed patients and normal controls.
Methods. Six patients with unipolar depression and six matched
controls were scanned while performing easy and hard Tower of London problems
in a one-touch computerized paradigm and
while performing a perceptuomotor control task.
Results. The patients in this study showed an expected
task-related performance deficit compared with normal subjects. In normal
subjects, the task engaged a network of prefrontal cortex, anterior cingulate,
posterior cortical areas and subcortical structures including the striatum,
thalamus and cerebellum. Depressed patients failed to show significant
activation in the cingulate and striatum; activation in the other prefrontal
and posterior cortical regions was significantly attenuated relative to
controls. Crucially, patients also failed to show the normal augmentation
activation in the caudate nucleus, anterior cingulate and right prefrontal
cortex associated with increasing task difficulty.
Conclusions. These findings provide evidence for cingulate,
prefrontal and striatal dysfunction associated with impaired task performance
in depression. The present results are consistent with a
central role of cingulate dysfunction in depression as well as suggesting
impaired frontostriatal function.